From 052969a6022a06414b11ab6fe294d5af01d20a59 Mon Sep 17 00:00:00 2001
From: Guido van Rossum <guido@python.org>
Date: Tue, 21 Jul 1998 14:24:04 +0000
Subject: Don't use calculations on values gotten from tell().  Also use a
 slightly different way to test for the existence of unread.

---
 Lib/rfc822.py | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/Lib/rfc822.py b/Lib/rfc822.py
index fc244c5..2e97ef4 100644
--- a/Lib/rfc822.py
+++ b/Lib/rfc822.py
@@ -125,7 +125,14 @@ class Message:
         self.status = ''
         headerseen = ""
         firstline = 1
+        startofline = unread = tell = None
+        if hasattr(self.fp, 'unread'):
+            unread = self.fp.unread
+        elif self.seekable:
+            tell = self.fp.tell
         while 1:
+            if tell:
+                startofline = tell()
             line = self.fp.readline()
             if not line:
                 self.status = 'EOF in headers'
@@ -160,10 +167,10 @@ class Message:
                 else:
                     self.status = 'Non-header line where header expected'
                 # Try to undo the read.
-                if hasattr(self.fp, 'unread'):
-                    self.fp.unread(line)
-                elif self.seekable:
-                    self.fp.seek(-len(line), 1)
+                if unread:
+                    unread(line)
+                elif tell:
+                    self.fp.seek(startofline)
                 else:
                     self.status = self.status + '; bad seek'
                 break
-- 
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